Hydrocarbon conversion



Patented Mer. 19,' 194s UNITED s'rATEs .PATENT ortica HYnnooAaBoN CONVERSION Herbert J. Passino, Englewood, N. I., assignor to The M. W. Kellogg Company, Jersey City, N. J., a corporation of Delaware Application March 14, 1942, Serial No. 434,734

(ci. 26o-671') 16 Claims.

' boron fluoride. The subject matter of this application is disclosed in part in prior application Ser. No. 395,973, filed May 31, 1941.

The production of the desired alkylated a`roy matic hydrocarbons in accordance with the process of this invention apparently occurs as a result of simultaneous dealkylation'of the aromatic hydrocarbons of higher molecular weight, such as more highly alkylated aromatic hydrocarbons, by

a lesser number of carbon atoms which thereupon alkylate the aromatic hydrocarbon previously alkylated to a lesser degree than the desired alkylated aromatic hydrocarbon. v

In the further description of the invention reference will be made specifically to the reaction of xylenes with benzene to produce toluene because toluene is highly important as an vingredient of motor fuels of high octane value and as a starting material in the preparation of other valuable materials, such as explosives. The reaction of xylenes with benzene to produce toluene provides an excellent example of this process in view. of

the extreme difficulty in which this reaction is effected by previously known methods as compared to other `similar reactions such as the reaction ofbenzene with diethyl benzene.

The reaction of xylenes and benzene toy produce toluene is lcarried out preferably in' the liquid phase in the presence of a catalyst essentially` comprising substantial amounts of boron trilinthe removal of alkyl groups therefrom and alkylation of the aromatic hydrocarbons previously alkylated to a lesser degree than the desired aromatlic hydrocarbons, by means of the alkyl groups formed by the dealkylation reactions.

Whilethe process of the invention is applicable to the treatment of mixtures of hydrocarbons to obtain a product consisting of a mixture of desired alkylated hydrocarbons, it will be described for purposes of clarity by reference to the production of a single alkylated aromatic hydrocarbon from aromatic hydrocarbons alkylated to a lesser degree and higher molecular weight aromatic hydrocarbons such as more highly alkylated aromatic hydrocarbons. For example,the production of toluene by the reaction of benzene and xylene will be referred to specifically inA the further description of the invention. Other specic examples are the production of xylenes through the reaction of toluene and trimethyl benzene. The invention is not limited. however, to the production of methylatedaromatic hydrocarbons, but includes also the productionof equivalent to over 5 weight per cent of the hydroalkylated hydrocarbons by reactions of ethylated hydrocarbons with hydrocarbons alkylated to a lesser degree, such as the reaction of benzene with diethyl benzene. The invention includes within its scope also reactions in which alkylated aromatic hydrocarbons having relatively long alkyl side chains or which have attached rings are dealkylated by the formation, from such side vchains or attached rings, of alkyl groups having oride' and hydrogen iiuoride. While the boron triiiuoridel and the hydrogen fluoride need not be present in the reaction zone in the form of a physical mixture, it is necessary that they .be available for simultaneous contact with the hydrocarboris undergoing reaction treatment whereby they function essentially as a single catalytic material. 'While the relative proportions of the hydrogen iiuoride and boron triiiuoride may vary within a considerable range, it is necessary that the hydrogen iluorlde be present in the reaction zone in a substantial quantity in relation to lthe proportion of hydrocarbon reactants present. This constituent of the catalytic material should be present in the reaction zone in an amount carbon reactants present and preferably in an amount equivalent to at least 10 weight per cent of the hydrocarbon reactants present. The quantity of boron fluoride in-contact with the hydrocarbon reactants and hydrogen iluoriderelative to the quantity of hydrocarbon reactants may vary within relatively wide limits buty ordinarily should be equivalent to approximately 5to 25 Weight per cent of the hydrocarbon reactants Conveniently, both the hydrogen iluoride and boron iluoride contacting the hydrocarbons are present in amounts equivalent to 5 to 25 weight per cent of the hydrocarbon reactants present.

Ordinarily, it is' desirable to maintain the reaction conditions such that the hydrocarbons and catalytic materials are substantially in the liquid phase. Alternatively, the hydrocarbons may be maintained in the liquid phase and the catalytic material contacted therewith while one or both are inthe vapor phase. 'I'he most favorable operating conditions appear to be approximately 200 to 400 F. and 30010 1000 pounds per square inch. The reaction time necessarily is the length of 'time required to eilect the desired reaction under the operating conditions selected. The reaction time depends a great deal upon the intimacy of contact between the catalytic materials and the hydrocarbon reactants. Conveniently, the reaction is carried out in the liquid phase, and the mixture of reactants and catalyst is beaten or stirred into an emulsion in which the desired intimate contact is effected. Convenient- 1y, the reaction is carried out in a continuous manner in which a portion ofa body of the emulsion of reactants is continuously withdrawn and` replaced with fresh supplies of hydrocarbon reactants and catalyst. The hydrocarbons withdrawn are fractionated to separate the desired alkylate product and otherfraetions suitable for recycling.

Preferably, the hydrocarbon reactant which' is aikylated to a lesser degree, in this instance benzene, is maintained in the reaction zone in considerable excess of the amount required to react with all of the more highly alkylated aromatic hydrocarbon reactant in order to promote formation of the desired alkylate product. For example, in the reaction of benzene with xylenes it is desirable to maintain the benzene in the reaction zone in considerable excess of the amount required to react with all the xylene to form toluene. A molar ratio of benzene to xylene oi at least 2:1 is desirable, and it is preferred that this ratio be 4:1 or higher.

Example I A reaction mixture consisting of approximately 529 parts by weight of benzene and 175 parts by weight of xylenes was intimately contacted with a catalyst consisting of 100 parts by weight of hydrogen fluoride and 50 parts by weight of boron fluoride. The mixture of hydrocarbons and catalyst was contacted under a pressure` of 650 pounds per square inch at a temperature of 300 perature of 400 mixture in accordance with the following reaction v Example 1I 82l parts by Weight of the :mene fraction recovered in Example I were mixed with 529 -parts lto comprise approximately 6 volume percent of toluene, 82 volume per cent of benzene and 12 volume per cent of material higher boiling than toluene and apparently including a substantial amount of unreacted xylenes. This production of toluene represents a yield of 25.5 per cent of the -theoretical maximum yield which could be obtained from the xylene fraction if it consisted entirely of xylenes. This production of toluene probably represents a higher percentage of the theoretical maximum yield 'since it is probable that the xylene fraction was not entirely made up of xylenes. However, since such xylenes as were in the xylene fraction treated in this .operation were materials unreacted in Example I, the total production of toluene in the two operations represents a yield equivalent to 61 per cent of the\ theoretical maximum yield of toluene obtainable by reacting all the xyienes present in accordance with the above reaction. This does not represent, however, the maximum yield obtainable since the tained additional convertible xylenes and since the quantity of the xylene fraction employed in Example 1i did not represent the total amount of such a material recovered from the product of Example I.

Apparently the i'luoride and boron fluoride the production of toluene in the foregoing examples. For example, when 705 parts. by weight of a hydrocarbon mixture consisting of per cent benzene, 3 per cent toluene and 1.*1 per cent xylenes was contacted withparts by weight of hydrogen iiuoride for 18 hours at 300 F., and 520 pounds per square inch pressure no additional toluene was produced. r102 parts by weight of a mixture of 50 per cent benzene, 'I per cent toluene and 43 per cent xylenes was treated at 400 F. and 940 pounds` per square inch pressure in the presence of parts by weight of hydrogen iiuoride for a period of 5 hours without the production of additional toluene. 706 parts by weight of a hydrocarbon mixture consisting of 'I0 per cent benzene, 4 per cent toluene and- 26 per cent xylenes was contacted for 8 hours at a tem- F. and a pressure of 1040 pounds per square inch with acatalyst consisting of 150 parts by weight of hydrogen fluoride and 20 parts by weight of nickel without the production of 'additional toluene. A hydrocarbon mixture similar to that treated in Example I was subjected to contact with a catalyst consisting of 100 parts of boron uoride for a period of 3 hours at a temperature of 300- F. and a pressure of 690 pounds per square inch without the production of any toluene.

The invention will be described in more detail, in connection with the reaction of benzene and xylenes to produce toluene, by referencefto the accompanying drawing which is a diagrammatic view in elevation of an arrangement of apparatus suitable for carrying out the invention. It is to be understood, however, that the -referen to the specic reaction of benzene and xylenes and the reference to the specific apparatus illustrated in the drawing are illustrative only of certain modications of the invention which is capable of other modifications. v

Referring to the drawing, benzene, ilowing presence of both the hydrogen was necessary to effect through line I, xylenes ilowing through line 2, and

a mixture of hydrogen fluoride-and boron iluoride, owing through line 3, are introduced into a suitable mixer Il. From mixer 4 the resulting mixture of hydrocarbon reactantsand catalyst is passed through line to a suitable reactor 6. In

reactor 8 thel mixture of reactants and catalyst is subjected to agitation to eiect intimate contact of hydrocarbon reactants. with each other and with the catalyst for a suiiicient length cf time toeilect the desired reaction. Agitation of the mixture may be effected by any suitable means for mixing or beating the mixture, or the mixture may be circulated continuously through .a closed circuit including a plurality of jets locatedwithin the reaction zone to eect intimate mixing of the material circulated through the means 22. At 22 the lvapors are cooled sufciently to eiect complete condensation of the benzene,

.and condensate thus obtained, together with any uncondensed material such as boron uoride, is transferred to reflux drum 23 through line 24. Benzene collected in drum 23 is withdrawn therefrom' through line 25, provided with pump 26, and introduced into line I for recycling lto the reaction zone. A portion of the benzene condensate may bediverted from line 25 through line 21 and returned t'o the upper portion of fractionator I5 as reflux. Therboron fluoride separated in drum 23 is withdrawn through line 28. Suitably, this material may be returned to the recircuit and in the zone into which the circulated material is injected.

A'portion of the mixture. of reactants and catalyst maintained in reactor 8 is withdrawn therefrom continuously through line I which connects with a settler 8. In settler 8 the mixture is permitted to separate into an upper hydrocarbon layer and a lower hydrogen uoride layer. Most of the boron iiuoride remains absorbed in the action zone through lin'e 29 which connects line 28 with line 3. L

'I'he condensate collected in the lower portion of fractionator I5 which includes unre acted xylene and higher-boiling hydrocarbons is withdrawn therefrom through line 30 which connects fractionator I5 with line 2 whereby mahydrogen iluoride layer, although a portion is absorbed in the hydrocarbon layer, and a portion may separate as a gas. .The latter portion of the boron uoride may be recycled directly to the reaction zone by means of line swhich' connects the upper portion of settler 8 with line 3.

The` lower liquid layer separated in settler 8 contains substantially al1 the hydrogen iiuoride, a large proportion of the boron iiuoride and includes also a complex of hydrogen iiuoride and aromatichydrocarbons. This layer of material is withdrawn from settler 8 through line I0 which connects with a second settler II. Line III is provided with suitable heating means I2 whereby the mixture passing through line I8 is heated suiilciently to decompose the complex with the release of aromatic hydrocarbons and hydrogen',

fluoride. The hydrogen iiuoride and boron uoride are vaporized by the `heat applied at I2 and separate in settler II from the remaining liquid. The mixture of hydrogen fluoride and boron fluoride vapors is recycled to the reaction zone from settler Il.through line I3 which connects settler II with line 3. The liquid in settler I II separates into a lower layer of sludge which small amount of hydrocarbons higher boiling than xylene, apparently through direct combination of benzene and xylene, it'may be desirable to further fractionate the material passing through line 30 before reintroduction into the reaction; zone to remove such high-boiling hydrocarbons,

and prevent the accumulation of these materials in the system. For example, all or a portion of the hydrocarbon iiowing throughline is diverted through line 35 and introduced into a fractionator 36. In fractionator 36 conditions of temperature and pressure are maintained to separate overhead a vapor fraction essentially comprising xylenes and a heavy liquid fraction which collects in the lower portion of fractionator 36. This relatively high-boiling material, which may comprise hydrocarbons such as anthracene, etc., is withdrawn from fr actionator 3B through line 31. A

is withdrawn through line' I4 and an upper layer comprising aromatic hydrocarbons released `by Y the decomposition of the complex.

The hydrocarbon layer separated in settler 8 is 4transferred therefrom. to fractionator I5 through line I8 by means of pump I'I'.- The hydrocarbon layer separated in settler I I is likewise transferred. to fractionator llilthrough line I8,

' provided with pump I9, which connects settler II with line IG.

In fractionator I5 the hydrocarbons introduced therein are subjected to fractionating conditions `of temperature and pressure effective 'to separate the hydrocarbons into a light fraction esvsentially consisting of benzene which-is withdrawn overhead, a heavy fraction essentially con-l sisting of unreacted xylenes and higher-boiling hydrocarbons which accumulate in the bottom of fractionator l5, and an intermediate fraction .essentially consisting of toluene which iswithdrawn from fractionator Itas aside cut through l 1ine'20. The benzene vapors are withdrawn overhead through line 2| which connects with cooling suicient amount of such high-boiling material.

is withdrawn from the system ,in .this manner to prevent its accumulation in the reaction zone. The high-boiling hydrocarbons withdrawn at 31 may be' subjected to further treatmentv for the recovery of lower-boiling aromatic hydrocarbons therefrom. For example, by simple heat treatment of this material substantial quantities of toluene as well as other hydrocarbons are Vrecovered.

The xylene vapors are-withdrawn overhead in fractionator 38 through line 38 which connect to reiiux drum 33. Line 38 is provided with cooling means II@ to eiect complete condensation of the xylene vapors-andthe resulting condensate aci cumulates in dra-m39. kA portion of this condensate is returned to the upper portion of fractionator 38 through line 4I as reflux, and the remainder is withdrawn through line 42'and introduced intoline 30 for recycling to the reaction zone.

In the reactor 8 the ratio of benzene to xylenes is maintained as high as practical to minimize the formation of sludge and to accelerate the re- `support, such as alumina.

action. In order to maintain a high ratio of benzene to xylene in reactors it is necessary to 'maintain a high ratio of such materials in the mixture introduced .through line into the 'reactor 5. VFor example, a' ratio of`4 parts by weight of benzene to 1 part by Weight of xylene in the desirable to facilitate the reaction inthe manner described. It is necessary, however, to supply to the system only theamountof benzene necessary to react with all the xylene since the excess of.

benzene is recovered for recycling through line 25.

The foregoing method for reaotingbenzene and xylenes is adapted to the treatment of such hydrocarbons obtained from any suitable source. The invention is, however, particularly adapted, especially in the reaction of benzene and xylenes,

' mixture introduced through line 5, or higher, is

' liquid constituents of the reaction mixture are head through line 5I and a condensate which is for use in connection with the catalytic aromatization treatment of aliphatic hydrocarbons containing the requisite number of carbon atoms per molecule wherein such aliphatic hydrocarbons are? converted to aromatic hydrocarbons by dehydrogenation and cyclization reactions.

Infaccordance withthis v'modification of the invention a hydrocarbon mixture, which may contain aromatic hydrocarbons but which also contains aliphaticand/orl olenic hydrocarbons having at least 6 to 8 carbon atoms per molecule, is introduced in'to the system through line 43 provided with pump 44. The hydrocarbon mixture thus introduced' may be a relatively narrow fraction containing aliphatic hydrocarbons having 6 i to 8- carbon atoms per molecule,'or it may be a fraction having a relatively wide boilingrange such as a heavy naphtha. Line 43 connects with the inlet of a V'heating coil housed in a suitable heater 45 vwherein the' hydrocarbon mixture is heated to a temperature of 850"v F. to 1050 F.,

preferably 950" F'. The outlet of the heating coil in heater 45 connects withline 46 by means of which the heated hydrocarbon mixture is introduced into reactor-4.1.

Reactor 41 is provided with a suitable catalytic material for effecting the desired -aromatization reactions. Catalytic material suitable for this purposeincludes the oxides of chromium and molybdenum, preferably mounted' 'on a suitable Reactor 41 may be maintained at atmospheric or subatmospheric pressure, but preferably at superatmospheric During-.the passage of the hydrocarbons throughreactor 41 aliphatic hydrocarbons having 6 to 8.or` more carbon atoms -per molecule are" converted to corresponding aromatic hydrocarbons such as benzene, toluene, xylene and higher-boiling aromatic hydrocarbons by dehydrogenation and cyclization reactions.l Hydro.-

carbons of 'this character which may be present in the hydrocarbon mixture introduced into reactor 41 apparently do not react to an appreciable extent in reactor 41 under the conditions described, and this treatmentis therefore applicable to mixtures containingsubstantial proportions of.

aromatic hydrocarbons as well as to mixtures sub- -stantiallyfreeof aromatic hydrocarbons.

' The degree of conversion of aliphatic hydrocarbons Ato aromatic hydrocarbons in reactor'41 is controlled by suitable regulations of temperature and space velocity. Substantial production of aromatic hydrocarbonsis associated with high v Vtemperatures and relatively low space velocities. Within the temperature range mentioned space velocities of. 0.1 to ,3.0 volumes of liquid per volume of catalyst space per hour are employed condensed. The resulting mixture is separated in separator 49 into a gas which is withdrawn overwithdrawn through line 52, provided with a pump 53.'l

The gas withdrawn through line 5I consists principally of hydrogen, and a portion thereof may be recycled through line 54, provided with a compressor 55,l to` line 43'in order to recycle hydrogen' t'o the reaction mixture' in the amount of 0.5 to 9, preferably 3.0 mols of hydrogen per mol of hydrocarbon reactants, The recycling'of hydrogen in this manner is advantageous, particularly when reactor 48 is maintained under a hydrogen pressure of 30 to 450 pounds per square inch, in maintaining the activity of the catalyst in reactor 48.

The condensatewitlidrawn from separator 49 through line 52 is introduced intol a fractionator 56. Infractionator 56 conditions'of temperature and pressure are maintained to separate fractions concentrated in benzene, toluene and xylenes, re-

spectively. A fraction concentrated in toluene and containing at most a minor proportion of other aromatic hydrocarbons is Withdrawn as a side out through line 51. This material may be treated in any suitable manner for extraction of toluene therefrom, for example, by extraction with phenol. The toluene fraction passing through line'51 may be introduced, afterbeing heated to a suitable temperature at 58, into extractor 59; In .extractor 59 the hydrocarbon mixture is passed upwardly in countercurrent contact withV a downwardly moving stream of phenol which absorbs'toluene from the hydrocarbon mixture. The extract containing the toluene is withdrawn through line 60 and lintroduced into stripper 6l for lthe regenertion of toluene therefrom.` Toluene thus separated is vwithdrawn overhead through line B2 as a product ofthe process. Solvent stripped of toluene is withdrawn from 4stripper 6l through line 63 and reintroduced into the upper portion of I 1 extractor 59. The hydrocarbon mixture containinga substantially reduced concentration of aromatic hydrocarbons is withdrawn overhead inextractor 59 through line 64. Suitably this mixture is recycled to the aromatizati'on process by a suitable connection of line 64 with line 43. The hydrocarbon fraction concentrated in respectto benzene and containing at most a minor proportion of other aromatic hydrocarbons is withdrawn from the fractionator 56 as aside cut through line 65 for use in the reaction of benzene withxylenes.

obtained in the form of the bottoms'irom frac- 4tionator "58 which are withdrawn therefrom through line 66. This fraction contains asubstantial proportion of xylenes and in addition some higher-boiling aromatic hydrocarbons such as poly methyl benzenes, etc. which are suitable for reaction with benzene to form toluene. Prefadvantageously. .Forex'ampla at the preferred desired vermisslble proportion of thebottoms The xylene fraction may be escasos l may be included in the xylene fraction by means of line et which connects line te with line ai.

The material uncondensed in fractionator 56, which consists essentially of hydrocarbons lower boiling than benzene is withdrawn overhead through line 69. A portion thereof is liquefied by passage through cooler l0, and the liquefied portion is separated in separator li. Uncondensed material is withdrawn from the process through line VE. Condensate separated in separater li is withdrawn therefrom through line '53. A portion of this condensate is returned to frac- `tionator tit as redux through line it.

xylene fractions is first treated to extract therefrom a concentrate essentially consisting of the desired aromatic hydrocarbon. Such concentration may be eected in any suitable manner, but preferably the general method outlined above for the extraction of' toluene at 59 is preferred. Consequently, line S5 is indicated as connected to a benzene extractor 59B which is generally similar in construction and operation to toluene extractor 50 and is similarly connected with a benzene stripper SEB. The benzene concentrate is withdrawn overhead from stripper SIB through line 'i which connects with mixer t, as described above. Similarly. line 6l connects with the xylene extractor SeX which is similarly connected with a xylene stripper BIX. The xylene concentrate is withdrawn overhead from stripper 86X through line 2 which connects with mixer as described above. The means provided for concentrating the toluene, benzene and xylenes are identical in the drawing, and similar reference numerals refer to similar apparatus, those applying to concentration of benzene being identified by the letter B and those applying to concentration of Xylene being identified by the letter X.

The hydrocarbon mixtures withdrawn from the upper portions of extractors 59B and 59X, substantially depleted in aromatic hydrocarbons. may be recycled suitably to the aromatization process as indicated by the connection of lines 80B and MIX with line Sli. cycled through line @d consist essentially of aliphatic hydrocarbons and may include a small proportion oi naphthenes all of which are suitable forfurth'er conversion treatment for the production of aromatic hydrocarbons.

The` invention has been' illustrated by reference to a modification thereof involving the reaction of benzene and xylenes to form toluene. -It is to be understood,l however, that the invention is not thus limited but is applicable also to other reactions of highly alkylated hydrocarbons with lower-boiling hydrocarbons to produce hydrocarbons of an intermediate degree of alkylation. For example, as mentioned above, benzene may be reacted with higher-boiling aromatic hydrocarbons such as trimethyl benzenes at the same time the reaction with xylenes is effected with the formation of toluene therefrom. The inven.

tion also includes the production of alkylated hydrocarbons by reaction of a hydrocarbon of a lesser degree of alkylation. with higher-boiling multi-ring aromatic hydrocarbons such as naphhigh yield of toluene, but it is to be understood Materials thus vrethat the improved method of producing allsyiated hydrocarbons by reaction of highly alkylated hydrocarbons or multi-ring aromatic hydrocarbons with hydrocarbons alkylated to a lesser degree,

such as benzene in the presence of hydrogen iluoride and boron fluoride, is of general application.

I claim:

l. The method of producing an alkylated aromatic hydrocarbon which comprises contacting an alkylated aromatic hydrocarbon o f higher molecular weight than said desired alkylated aromatic hydrocarbon and an aromatic hydrocarbon of lower molecular weight than said desired alkylated aromatic hydrocarbon at elevated temperature simultaneously with hydrogen fluoride and boron fluoride.

2. The method of producing an alkylated aromatic hydrocarbon which comprises contacting an alkylated aromatic hydrocarbon of higher molecular weight than said desired alkylated aromatic hydrocarbon and benzene at elevated temperature simultaneously with hydrogen fluoride and boron fluoride.

3. The method of producing toluene which comprises contacting xylene and benzene at elevated temperature simultaneously with hydro' 6. The method of producing toluene which comprises contacting xylene and benzene at a temperature of 200 to 400 F. and at a pressure of` 300 to 1000 pounds per square inch simultaneously with hydrogen fluoride and boron uoride.

'7. The method of producing a methylated aromatichydrocarbon which comprises contacting an aromatic hydrocarbon more highly methylated than said desired methylated aromatic hydrocarbon and an aromatic hydrocarbon of lower molecular weight than said desired methylated aromatic hydrocarbon at elevated temperature simultaneously with hydrogen fluoride and boron fluoride. 4

8. The method of producing methylated aromatic hydrocarbons which comprises acting upon highly methylated aromatic hydrocarbons to separate methyl groups therefrom in the presence of hydrogen fluoride and boron fluoride and a hydrocarbon of lower molecular Weight than said desired methylated aromatic hydrocarbons. f

9. The method for producing xylenes which comprises contacting toluene and poly-methylated benzenes having more than two attached methyl groups at elevated temperature simultaneously with hydrogen fluoride'and boron fluoride tacting a polymethylated aromatic hydrocarbon more highly methylated than said desired methylated aromatic hydrocarbon and an aromatic,A

hydrocarbon of lower molecular weight than said desired methylated aromatic hydrocarbon at a temperature of 290 to 400 F. simultaneously with hydrogen fluoride and boron fluoride.

1l. A process for converting a polyalkyl aromatic hydrocarbon to an alkyl aromatic hydrocarbon having a fewer number of alkyl groups per molecule, which comprises treating a polyalkyl aromatic hydrocarbon in admlxture with a substantial molecular excess of an aromatic hydrocarbon having at least two alkyl groups per molecule fewer than said polyalkyl aromatic hydrocarbon and in the presence of hydrogen fluoride and boron uoride to produce an alkyl aromatic hydrocarbon having fewer alkyl groups per molecule than said polyalkyl aromatic hydrocarbon, and recovering from eiliuents of said treatments an alkyl aromatic hydrocarbon so produced.

l2. A process for converting a polymethyl aromatic hydrocarbon to a methyl aromatic hydrocarbon having a fewer number of methyl groups per molecule, which comprises treating a polymethyl aromatic hydrocarbon in admixture with a substantial molecular excess of an aromatic hydrocarbon having at least two methyl groups per molecule fewer than said polymethyl aromatic hydrocarbon and in the presence of hydrogen fluoride and boron fluoride to produce a methyl aromatic hydrocarbon having fewer methyl groups per molecule than said polymethyl aromatic hydrocarbon, and recovering from eflluents of said treatment a methyl aromatic hydrocarbon so produced.

13. The method of producing a methylated aromatic hydrocarbon which comprises contacting an aromatic hydrocarbon more highly methylated than said desired methylated aromatic hydrocarbon and benzene at elevated temperature simultaneously with hydrogen fluoride and boron fluoride.

14. The method of producing methylated aromatic hydrocarbons which comprises acting upon highly methylated aromatic hydrocarbons to separate methyl groups therefrom in the pres- 35 ride.

ence of an aromatic of lower molecular weight than the desired methylated aromatic hydrocarbon and a catalyst comprising a liquid mixture of a major proportion of hydrogen uoride and a minor proportion of boron fluoride.

15. The method of producing toluene which comprises contacting a hlghermolecular weight alkylated aromatic hydrocarbon and benzene at elevated temperature simultaneously with hydrogen fluoride and boron uoride, said benzene being presentin a substantially greater amount than said higher molecular weight aromatic hydrocarbon.

16. .The method of producing an alkylated aromatic hydrocarbon which comprises contacting an allqlated aromatic hydrocarbon of higher molecular weight than said desired alkylated aromatic hydrocarbon and an aromatic hydrocarbon of lower'molecular weight than said desired alkylated aromatic hydrocarbon at elevated temperature with a catalyst comprising a liquid mixture of a major proportion of hydrogen uoride and a minor proportion of boron iluo- HERBERT J. passino. 

